In multistage rotary machines used for energy conversion, for example, a fluid is used to produce rotational motion. In a gas turbine engine, for example, a gas is compressed in a compressor and mixed with a fuel in a combustor. The combination of gas and fuel is then ignited for generating hot combustion gases that are directed to turbine stage(s) to produce rotational motion. Both the turbine stage(s) and the compressor have stationary or non-rotary components, such as vanes, for example, that cooperate with rotatable components, such as rotor blades, for example, for compressing and expanding the working gases. Many components within the machines must be cooled by cooling fluid to prevent the components from overheating.
Leakage between hot gas in a hot gas flow path and cooling fluid (air) within cavities in the machines, i.e., rim or vane cavities, reduces engine performance and efficiency. Cooling air leakage from the cavities into the hot gas flow path can disrupt the flow of the hot gases and increase heat losses. Further, the more cooling air that is leaked into the hot gas flow path, the higher the primary zone temperature in the combustor must be to achieve the required engine firing temperature. Additionally, hot gas leakage into the rim/vane cavities yields higher vane and vane platform temperatures and may result in reduced performance.